An inflator for use in an inflatable vehicle occupant protection system. The inflator includes a pressure vessel having an opening formed therein. A quantity of relatively unreactive pressurized gas is stored in the pressure vessel. A quantity of a gas generant composition is positioned in an interior of the pressure vessel and in fluid communication with the pressurized gas. An igniter is positioned proximate the gas generant for initiating combustion of the gas generant. A rupturable, fluid-tight seal is positioned to seal the opening in the pressure vessel for maintaining the pressurized gas within the pressure vessel prior to activation of the igniter. Activation of the igniter results in combustion of the gas generant. Pressure from the combustion gases, in combination with the pressure of the gases stored under pressure in vessel, cause the burst disk to rupture, providing an inflation gas to an associated vehicle airbag, for example.
